[Geoinfo] Conferencia Dr. Archer

[Ana]

La Asociación Argentina de Sedimentología y el Departamento de Ciencias Geológicas
de la UBA tienen el agrado de invitar a la conferencia del Dr. Allen W. Archer:


"TIDAL RHYTHMITES IN MODERN AND ANCIENT HYPERTIDAL ESTUARIES"

 Aula Amos del Departamento de Ciencias Geológicas, FCEyN, UBA. Ciudad
Universitaria, Pabellón II. Ciudad Autónoma de Buenos Aires.

 Viernes 19 de Marzo, 14 hs.


El Dr. Allen W. Archer (PhD University of Indiana) es actualmente profesor de
Estratigrafía y Sedimentología en la Univesidad de Kansas, USA. Se ha especializado
en ciclicidad y ritmicidad en depósitos originados por mareas (tidal rhythmites), de
edades que van desde el Precámbrico hasta el presente, particularmente en estuarios
con rangos de mareas extremos.


Resumen de la conferencia:

Tidal rhythmites, which exhibit systematic variations in lamina thickness, are most
common in hypertidal estuaries. Modern examples include the Bay of Fundy in eastern
Canada (tidal range >13 m), Ungava Bay in northeastern Canada (>12 m), Bay of Mont
Saint Michel in France (>11.5 m), estuaries along the Atlantic coast of southern
Argentina (>11 m), and Cook Inlet in south-central Alaska , USA (>10 m). These
modern examples provide analogs for ancient rhythmites, which have been documented
from the Proterozoic and Phanerozoic eons. Within the spectrum of astronomically
forced cycles, short-term periods exhibited by tidal rhythmites include semi-daily,
daily, half lunar month (neap-spring), and several lunar monthly cycles. All of
these periodicities have been reported from modern and ancient of tidal rhythmites.
Short-term tidal periods have quite consistent magnitude and frequency and thus can
directly affect sedimentation. Over geologic time, however,
tidal periods have changed. Examples of very ancient rhythmites indicate that the
paleotidal day was significantly shorter and that there were more solar days per
year. The rates of sedimentation within hypertidal estuaries can be very high,
particularly in the fluvio-estuarine transitional zones. Because of the high
turbidity and high sedimentation rates, sediment reworking by the biota can be
limited. Thus, bioturbation is minimal. These deposits are dominated by physical
sedimentary structures, such as tidal bedding, ripples, and thin laminae.


-- 
Este mensaje ha sido analizado por MailScanner
en busca de virus y otros contenidos peligrosos,
y se considera que está limpio.

------------ próxima parte ------------
Se ha borrado un adjunto en formato HTML...
URL: http://tango.gl.fcen.uba.ar/pipermail/geoinfo/attachments/20100317/c9879ad8/attachment.htm